Candida albicans is the leading fungal pathogen of humans, causing life-threatening infection in immunocompromised individuals. Treatment of candidiasis is hampered by the limited number of antifungal drugs. The triazoles are the largest class of antifungal drugs in clinical use. They inhibit lanosterol 14-demethylase (Erg11). The therapeutic efficacy of triazoles is compromised by the emergence of drug resistant strains. C. albicans can acquire triazole resistance by multiple distinct mechanisms, including mechanisms to cope with drug-induced cellular stresses. Upc2, a transcriptional regulator of ergosterol biosynthesis pathway genes, is critical for resistance to triazoles. We find that Cph2 is also a regulator of ergosterol biosynthesis and misregulation of Cph2 leads to altered drug sensitivity. How Upc2 and Cph2 are regulated in C. albicans is unclear. Here we propose to use chemical approaches to dissect regulatory mechanisms for Cph2 and Upc2. Aim 1 identifies small molecules that target transcriptional regulation of ergosterol homeostasis. Aim 2 identifies protein targets of selected hit compounds in C. albicans by chemical genomics approaches. Aim 3 will be target verification and functional characterization in C. albicans. Identification of smal molecules and their targets will lead to the discovery of novel pathways and mechanisms that control ergosterol homeostasis and triazole resistance. PUBLIC HEALTH RELEVANCE: Candida has emerged as a significant human pathogen, causing life-threatening infection in immunocompromised individuals. Treatment of candidiasis is hampered by the limited number of antifungal drugs and the emergence of drug resistance. Development of novel combinatory drug therapy will help fight against Candida infections and lower the level of drug toxicity to people.